1. Field of the Invention
The present invention relates to a pulse wave detecting apparatus including a pulse wave sensor and, in particular, to the art of pressing the pulse wave sensor on a body surface of a living subject.
2. Related Art Statement
There is known a pulse wave detecting apparatus including a pulse wave sensor having a press surface in which one or more pressure sensing elements are provided and which is adapted to be pressed against an artery of a living subject via the body surface or skin above the artery. The detecting apparatus detects, by the sensor, a pressure pulse wave produced from the artery of the subject. Usually, air pressure is utilized to press the pulse wave sensor on the body surface of the subject. One example is disclosed in Unexamined Japanese Patent Application (filed by the Assignee of the present application) laid open under Publication No. 3-7139. The disclosed pulse wave sensor is fixed to an outer face of a flexible diaphragm provided in a container-like housing such that the sensor is displaceable relative to the housing. When a pressurized air is supplied from an air pump via piping to a pressure chamber defined by the housing and the diaphragm, the diaphragm is inflated and accordingly the pulse wave sensor fixed to the diaphragm is advanced out of the housing so as to be pressed on the body surface of the living subject.
However, the above-mentioned conventional pulse wave detecting apparatus suffers from various problems resulting from the use of an air pump and a piping. In particular, in the case where the prior apparatus is used to detect a pulse wave from a living subject who is undergoing an exercise test or to monitor for a long period of time a pulse wave of a patient who is receiving medical treatments at his or her home, without restricting his or her daily activity, it has been proposed that the air pump be mounted on the housing, for preventing the piping from being stretched out and thereby moving the pulse wave sensor out of position on the subject, or for broadening the sphere of action of the patient. With this arrangement, however, the size and weight of a portion of the pulse wave detecting apparatus to be worn on a living subject, are enlarged and increased. Additionally, the noise of the air pump produced during operation thereof may disturb the sleeping of a living subject.